LOW OIL PRESSURE NEED HELP!

[Powerstroker7.3Ldiesel]

ok i have a 2001 7.3L i sent it off to get bored 20 over and my heads port and polished. it came back i put it all together and put it in my truck. I am only getting 5psi at idle and 39 at 3300 rpms. I have changed the pump, the oil cooler, the oil pressure regulator, the bypass valve, and the anti drain back check ball. WHAT ELSE COULD IT BE!? something inside the engine? i need all the help i can get. thanks for any info.